4(>6 Illinois State Laboratory of Natural Histoinj. 



with that of the muscular sac inclosing it, while the lumen 

 of the sperm-duct which passes through it is surrounded by 

 an epithelial layer continuous at the inner end with that of the 

 muscular duct, and at the tip with the epithelium covering 

 the outer surface. Between these two epithelial layers is ;i 

 tissue composed of elongated cells, slightly inclined to the 

 long axis, which connect the inner and outer epithelial layers. 

 The cells are not as closely packed as are those of muscle 

 layers, and the tissue which they compose probably corre- 

 sponds to the "fibrous tissue" which is present in the atrium 

 of E.frigidus. 



A pair of large elongated sperm-sacs extends backward 

 from the posterior septum of IX through twelve to eighteen 

 somites. A sperm-reservoir and its connecting ducts are 

 situated in the anterior part of each, and in one specimen the 

 spermatheca j also were included in the anterior part of the 

 sperm-sacs (PI. XLL, Fig. 3). The posterior part of each 

 sperm-sac is constricted by the septa, and in the specimens 

 studied the cavities were filled with spermatozoa. 



One pair of ovaries is present in the anterior part of X. and 

 a pair of oviducal funnels is borne on the posterior septum of 

 that somite, opening to the exterior in the groove between X 

 and XI. Large ova were present in but one specimen and 

 were contained in X. From the posterior part of that somite 

 a thin sheath of cells extends backward, enveloping the sperm- 

 sac, and including in the cavity between them the posterior 

 pair of lateral vessels of X. The posterior limits of this 

 sheath have been difficult to determine, and there is certainly 

 no appreciable space between it and the posterior end of the 

 sperm-sac, neither have any signs of ova been found within 

 it. It may be, however, that it represents an ovisac into which 

 ova might pass at a later stage of development. 



There is one pair of spermathecse, opening on the posterior 

 part of the ventral surface of somite VIII. These organs are 

 unusually long and much differentiated in their structure. 

 In two specimens they push the septum VIII/IX backwards 

 into IX, forming contorted masses, while in the other speci- 

 men each spermatheca extends posteriorly into the cone- 



